Generations ago, Republicans abandoned their assigned role — which was rarely real — as the party of pain that raised taxes to pay for popular Democratic spending programs. Now, in an era of low interest rates — actually, or almost, negative — the assumption is that deficits do not matter as long as the interest rate for servicing the national debt remains lower than the rate of economic growth, so the ratio of debt to GDP declines. At long last, for humanity, or at least the American portion, the table has been set for a free lunch.

This arms the political class with a theory that justifies them in doing what they would do anyway — give grateful voters government goods and services partially paid for by nonvoters: future generations. Remember, there are just two ways to fund a government: current taxes and future taxes. (The latter can include the stealthy tax of inflation: Borrow dollars worth X, repay with dollars worth X minus Y.)

Complacency about today’s soaring debt, and about rolling over $10 trillion or so of it annually, requires only the assumption that very low interest rates will (unlike, say, the Roman, Habsburg, Ottoman, British and Soviet empires) continue forever. So, an old jest is now a fundamental principle: The first law of economics is that scarcity is real, and the first law of politics is to ignore the first law of economics.